Seats of this type are disclosed in Japanese Utility Model Laid-Open Nos. 174462/1986 and 101850/1984.
The former Japanese Utility Model Laid-Open No. 174462/1986 discloses an arrangement in which a space is provided within a lower portion of a seat back, a hip support being accommodated within the space in such a manner as to be capable of being moved forwardly with its lower portion serving as a fulcrum, and when an occupant assumes a seated position in which his hip is moved forwardly, the hip support is moved forwardly so as to project away from the front surface of the seat back, thereby allowing the occupant's hip to be supported by means of this projecting portion. With this arrangement, when the occupant feels that the support of this hip is insufficient, it is necessary for him to rise up and seat himself again after moving the hip support to another position.
In the latter Japanese Utility Model Laid-Open No. 101850/1984, an arrangement is disclosed in which a space is provided within a lower portion of a seat back, a hip support being disposed within the space in such a manner as to be pivotable back and forth with an upper portion thereof serving as a fulcrum, and a seat plate is connected to a lower portion of this hip support by means of a hinge in such a manner as to be movable back and forth upon a seat cushion. With this arrangement, the occupant is seated upon the seat cushion through means of the seat plate. Accordingly, when the occupant feels that the support of his hip is insufficient, it is necessary for the occupant to rise up, move the hip support forwardly by pulling the seat plate in the forward direction, and then be seated again.
Thus, with the above-described two examples of the prior art, a drawback is encountered in that the occupant cannot adjust the position of the hip support while being seated.